Imidazole couplers for two component diazotype systems

ABSTRACT

Diazotype systems and method of diazotype reproduction are provided, the systems including as the coupler compound an imidazole coupler having the formula;   WHEREIN R1 is a hydrogen atom or an alkyl radical; R2 is a hydrogen atom, an alkyl radical, a thioalkyl radical, a sulfamido radical, a carbonylamino radical or an aryl radical; and R3 and R4 can be the same or different and are selected from the group consisting of a hydrogen atom, a carbonyl amino radical, an alkoxycarbonyl amino radical and an aryl radical; one of the groups represented by R1, R2, R3 or R4 optionally being a divalent bridging radical forming a bis-imidazole compound. Positive prints ranging in color from reddish-brown to violet red can be obtained.

United States Patent [191 Buisine et al.

[ Oct. 7, 1975 IMIDAZOLE COUPLERS FOR TWO COMPONENT DIAZOTYPE SYSTEMS [75] Inventors: Abel Buisine; Renaud de Torsiac,

both of Arques la Bataille, France [30] Foreign Application Priority Data Apr. 20, 1972 France 72.13898 [52] US. Cl 96/91 R; 96/49; 96/75 [51] Int. Cl. G03C 1/58 [58] Field of Search 96/91 R, 75, 49

[56] References Cited UNITED STATES PATENTS 2,212,959 8/1940 Schmidt et al. 96/91 R 2,532,744 12/1950 Straley 96/91 R 2,548,845 4/1951 Neumann 96/91 R 2,971,842 2/1961 Moore et a1. 96/91 R 3,140,181 7/1964 Wilders et al..... 96/91 R 3,199,982 8/1965 Kashiwabara..... 96/91 R 3,248,220 4/1966 Van Rhijn 96/91 R 3,294,542 12/1966 Sus et al 96/91 R 3,386.828 6/1968 Slimowicz 96/91 R 3,754,916 8/1973 Winslow et a1. 96/91 R Primary ExaminerCharles L. Bowers, Jr. Attorney, Agent, or FirmShermans & Shalloway [57] 1 ABSTRACT Diazotype systems and method of diazotype reproduction are provided, the systems including as the coupler compound an imidazole coupler having the formula;

wherein R is a hydrogen atom or an alkyl radical; R is a hydrogen atom, an alkyl radical, a thioalkyl radical, a sulfamido radical, a carbonylamino radical or an aryl radical; and R and R can be the same or different and are selected from the group consisting of a hydrogen atom, a carbonyl amino radical, an alkoxycarbony] amino radical and an aryl radical; one of the groups represented by R R R or R optionally being a divalent bridging radical forming a bisimidazole compound. Positive prints ranging in color from reddish-brown to violet red can be obtained.

3 Claims, No Drawings IMIDAZOLE COUPLERS FOR TWO COMPONEN DIAZOTYPE SYSTEMS BACKGROUND OF THE INVENTION The present invention relates to diazotype materials including novel coupler compounds and methods of using the same.

Diazotype' printing processes have been used for many years and have been used in several forms, most notable of which are the negative diazotype processes and the positive diazotype processes. Exemplary of the former process is the image-wise exposure of a diazo film layer containing a light-sensitive diazonium compound and a mercurous salt. This process results in grainless silver images of high resolving power and requires physical development in which exposure requires only a far smaller quantity of light energy than several other diazotype processes. The negative type processes have not, however, become commercially successful.

The positive diazotype processes have become increasingly popular due to their high contrast and the short and simple after treatments required to obtain direct positive copies which are particularly adaptable for such uses as the reproduction of line originals such as tracings and in preparation of maps and similar sketches. Typical of the positive diazotype processes are the two component or dry treatments in which a suitable substrate is coated with a light-sensitive diazonium compound and a coupler compound, usually in the presence of a stabilizing acid to prevent premature coupling; after exposure to light through a transparency of the original work, development takes place by contact with an alkaline material, generally anhydrous ammonia. In the semi-dry process, the substrate only contains the photosensitive diazonium compound; after image-wise exposure to light, the substrate is developed by contact with an alkaline developing solution which contains the coupler compound. The third most widely used positive diazotype process is the heat developable process in which the diazonium compound and the coupler compound are again combined on the substrate in an acid medium containing a base releasing agent which, after the substrate is image-wise exposed to a light source, a heat treatment is administered which results in the production of an alkaline environment which allows the coupler compound and diazonium compound to react and form the dye image.

Each of the different positive processes, however, have been subject to various drawbacks. For example, the dry processes are subject to the problem that with most diazonium compounds and couplers, the waterfastness of the prints obtained is unsatisfactory for many purposes because of the problems in storage of the finished product and the inability to wash the finished product. Moreover, in the production of red or reddish brown prints, the most typically used couplers, amides of 3,5-dihydroxy benzoic acid or the thiazole or selenazole derivatives of these amides, only exhibit slight water solubility and makes the use of these compounds difficult.

SUMMARY OF THE INVENTION It has now been found that the above disadvantages and problems inherent in diazotype materials, particularly two component diazotype materials, can be elimiwherein R is a hydrogen atom or an alkyl radical, preferably C C I alkyl; R is a hydrogen atom, an alkyl radical, preferably C,C alkyl, a thioalkyl radical, preferably containing 1 to 8 carbon atoms in the alkyl group, a sulfainido radical, a carbonylamino radical, or an aryl radiCaL-preferably C C aryl, most preferably phenyl; and R and R can be the same or different and are selected from the group consisting of a hydrogen atom, a carbonylamino radical, an alkoxycarbonylamino radical, preferably containing 1 to 8 carbon atoms in the alkoxy group, and an aryl radical, preferably C C aryl, most preferably phenyl; and wherein one of the groups represented by R R R or R can be a divalent bridging radical forming a bisimidazole compound. These coupler compounds allow the production of strongly contrasting red prints, ranging from reddish brown to violet red, while providing satisfactory water-fastness of the developed prints and good preservation thereof. These novel couplers can be used with most of the diazo compounds used in diazotype processes and are particularly suitable with diazonium compounds derived from diazotized paraphenylene diamine.'

The coupler materials of the present invention can be used alone or, when other shades and colors are desired, used with other conventional diazotype coupler materials. These new couplers are also capable of producing prints of particularly satisfactory line density and covering power and are therefore, particularly suitable for use with other couplers which result in dyes of printing shade on brown for making counter negatives.

Accordingly, it is an object of the present invention to provide novel coupler compounds, i.e., imidazole couplers, for use in diazotype materials which exhibit improved water-fastness and storage capabilities.

It is also an object of the present invention to provide a method of developing prints using a diazotype material incorporating these new coupler materials.

It is a further object of the present invention to provide diazotype materials, i.e., papers, films and the like, which can be used to develop highly contrasting reddish brown to violet red prints by development with anhydrous ammonia.

Still further objects of the present invention will become more apparent from the following detailed description thereof.

DETAILED DESCRIPTION OF THE EMBODIMENTS According to the present invention, novel coupler compounds formed from imidazoles have been found to provide strongly contrasting reddish colors which exhibit good storagability and water-fastness. These coupler compounds can be used with most conventional light-sensitive diazonium compounds in one or two component diazotype printing processes, preferably two component processes.

In the two component diazotype system, any suitable support or base layer will have an acid stabilized mixture of at least one light-sensitive diazonium compound and at least one coupler compound selected from the imidazole compounds of the present invention (with or without additional conventional coupler compounds) applied to its surface by any conventional means, e.g., coating, spraying, painting, etc. and in fact, the diazoas reacting a-dicarbonyl derivatives with ammonia and an aldehyde; the methods described in Chemistry of Carbon Compounds of E. H. Rodd, Elsevier Publishing Company, Tome IV-A, Heterocyclic Compounds, pages 286-291 are also suitable for forming these compounds.

Various imidazole coupler compounds of the present invention are presented in the following table:

nium compounds can be impregnated throughout the support or base material.

The novel imidazole coupler compounds can be used in any diazotype printing process wherein a positive print of an original containing image areas and transparent non-image areas is produced by placing the original over a photosensitive layer of a diazonium compound carried on a base layer and subjecting the base layer to image-wise exposure of light whereby the photosensitive layer of the diazonium compound is decomposed only under the transparent areas of the original and during the subsequent development of the nonexposed image area of the photosensitive layer, the diazonium compound reacts with at least one of the novel imidazole coupler compounds.

In the two component process, any conventional base layer, such as paper used for heliography or the like, is coated with at least one light sensitive diazonium compound and at least one coupler compound selected from the imidazole compounds of the present invention, the particular compounds selected depending, of course, on the color of the dye-image desired in the finished print. In order to prevent premature reaction between the diazonium compounds and the coupler compounds, an acid stabilizer is added to the mixture to give an acidic pH. Similarly, any other conventional additives can be included with the coating. Typical additives'include, for example, antioxidants, image intensifies, humectants, wetting agents, solvents, etc.

A transparency of the original containing transparent non-image areas and non-transparent image areas is placed over the coated base layer and subjected to light irradiation, such as by a mercury lamp. Any light sensitive diazonium compounds in the base layer are thus decomposed only in the areas corresponding to the non-image transparencies of the original. Subsequently, during the development of the print, the base layer is contacted with an alkaline medium, such as ammonia or the like, to neutralize the stabilizing acid and create a pH range in which the reaction between the diazonium compound and the coupler compound can take place to form the finished print.

The imidazole coupler compounds of the present invention are prepared by conventional processes, such The preferred imidazole coupler compounds include 2-methylmercaptoimidazole, 2-ethylmercaptoimidazole, bis-(2-imidazolyl)-l,S-dithiopentane, 4- acetylaminoimidazole, 2-phenyl 4- acetylaminoimidazole hydrochloride, and 1,2-dimethyl 5-ethoxycarbonylaminoimidazole.

By proper selection of the substituents carried by the imidazole molecule and by judiciously selecting the diazonium compound the desired color of the formed dye, in the range of reds varying from violet to brown can be achieved.

Any conventional light-sensitive diazonium compound can be used with the imidazole coupler compounds of the present invention. The following diazonium compounds may be noted as typical: 4-(NzN-dialkyl amino)benzene diazonium chloride, e.g. 4-(NzN- diethyl amino) benzene diazonium chloride; 4-(N1N- diethyl amino) benzene diazonium chloride fluoroborate; 4-benzyl amino 2:5 diethoxy benzene diazonium chloride; 4-morpholino benzene diazonium chloride; 4(N-benzyl-N-ethylamino) benzene diazonium chloride; 2,5-(diethoxy-4,4 ethoxy-phenyl) benzene diazonium chloride; 2-ethoxy-4-diethyl amino benzene diazonium chloride; 3-ethoxy-4-morpholino benzene diazonium chloride; 2-chloro-4-N-benzyl-N-methylamino- 5-p-chloro-phenoxy benzene diazonium chloride; 2,5- dialkoxy-4 arylmercaptobenzene diazonium chloride, e.g. 2,5-diethoxy-4-p-phenylmercaptobenzene diazonium chloride.

Diazo compounds derived from diazotized paraphenylene diamine, e.g. paradiethylamino benzene diazonium chloride, 4-morpholine 2, S-diethoxy benzene diazonium chloride, are particularly suitable for use with the imidazole couplers of the present invention.

The diazonium compounds are preferably used as diazonium salts, e.g. diazonium chloride, or the metal chloride double salt thereof.

In order to prevent premature coupling of the lightsensitive diazonium compound and the coupler compound, stabilizing acids are usually incorporated into the diazo-type material. Any conventional acid stabilizer may be used, for example, citric acid, tartaric acid, boric acid, acetic acid, phosphoric acid, succinic acid, benzoic acid, benzene sulfonic acid, naphthalene trisulfonic acid, sulfosalicyclic acid. Other stabilizing compounds such as aluminum sulfate or alum are also suitable and can be combined with any of the conventional stabilizing acids.

The diazo-type material containing the photosensitive diazonium compound, and in the two component system, the imidazole coupler compound, should also include an active antioxidant to prevent the discoloration of the azo dyes resulting from the action of light and air or in'the case of cellulose base materials inhibit the oxidizing processes which result in reduction of mechanical strength and increase of brittleness and darkening of the base layer. Thiourea has been found to be one of the most effective antioxidants and its use is preferred. Other suitable antioxidants include, for example, hydroquinone, hydroxylamine, pyrogallol, Rochelle salt, tartaric acid, thiosulphate, oxalic acid, and citric acid. 0

Other additives which may be incorporated into the diazo-type material include image intensifiers, such as ammonium sulfate, nickel sulfate or zinc chloride; humectants such as glycols or glycerine; wetting agents such as sulfates and sulfonates, e.g., lauryl-sulfate, alkyl benzene sulfonate; volatile solvents may also be included in the diazo-type compositions of the present invention, for example, methanol, ethanol, acetone, methyl ethyl ketone, ethyl acetate, ethylene glycol monomethyl ether, etc.

The compositions containing the light-sensitive ac tive diazonium compound and any of the other additives are coated in the usual manner upon any suitable base layer. Suitable bases for the diazo-type materials include transparent paper, varnished films, such as cellulose acetate or polyethylene terephthalate, or plastic films coated with a matting layer and, in general, any suitable heliographic paper material.

Surface-improving substances, such as finely divided silicon dioxide, aluminum oxide, barium sulfate, rice starch, etc. can be added to the base layer. Similarly,

binders, such as polyvinyl alcohol, polyvinyl acetate, gelatin, gum arabic, etc., can also be used.

As previously noted, the imidazole coupler compounds of the formula wherein R,, R R and R are as defined above, may be used in any of the diazo-type printing processes and, preferably the two component process in which a base layer carries an acid stabilized mixture of at least one diazonium compound and at least one coupler compound selected from the imidazole compounds of the present invention. The imidazole couplers may be combined with any other conventional coupler compound, such as: resorcinol, octylresorcinol, 2,5-xylinole, phluoroglucinol, betanaphthol, 2,3-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,3-dihydroxynaphthalene--sodium sulfonate, 2-amino-8-naphthyl-3,6- disodiumsulfonate, 2-naphth0l-3,6-disodium sulfonate, oz-resorcyclic acid amide, 2,3-hydroxy naphthalic-acidhydroxyethylamide, 2,2,4,4-tetrahydroxybiphenyl,

6 phluoroglucinol-carboxylic acid, 1,7-aminonaphthyl-2- hydroxy-8-biguanide, m-hydroxyphenyl-urea, acetoacetanilide, 7-hydroxyl Z-naphthaimidazole, and l-phenyl-3-methyl-S-pyrazolone.

In selecting the imidazole compound, it is preferable to have at least one of R R R or-R other than a hydrogen atom.

The following examples illustrate both the method of preparing the imidazole coupler compounds of the present invention and diazo-type compositions including the imidazole couplers and the methods of use of these compositions in diazo-type printing processes. It

is, of course, realized that these examples are merely illustrative of the general principles of the present invention and are in no way to be considered limiting thereof.

is applied to blank paper of the quality usually used for making heliographic papers which has been previously coated with a finish of colloidal silica and polyvinyl acetate. 1

The paper thus coated is dried and exposed under a transparent original to the light emitted by a mercury vapor lamp. After development with ammonia, well contrasted prints are obtained with red lines on a white I background.

These prints are distinguished by the fact that the dye does not dissolve when they are immersed in water.

The 2-methylmercaptoimidazole (compound 2) is prepared in two stages in the following way:

1. Diethyl amino acetal, NH CH CH (OC H is made to react in the presence of potassium sulfocyanide and hydrochloric acid to obtain Z-mercaptoimidazole (compound 1 )(J ones, Journal of American Chemical Society 1949, 71, 4000).

2. Methyl iodide is then made to react in the 2-mercaptoimidazole to obtain. 2-methylmercaptoimidazole as described in Marckwald, Chemische Berichte 1892, 25, 2360. The melting point of this product is C; its theoretical proportion of nitrogen: N%, 24.54; its theoretical proportion of sulfur: 8%, 28.09.

Compounds 3 and 5 are prepared in a similar way.

EXAMPLE 11 Blank white paper of the quality usually used in heliographic paper industries is coated with an aqueous solution of the following composition:

Citric acid 5g Thiourea 5g Ethyl alcohol 3cc Triethylene glycol 3cc 4-acetylaminoimidazole (formula 8) lg Double chloride of zinc and 4-morpholino 2,5-diethoxy benzene diazonium 2g Zinc chloride 5g Water lOOcc After drying, this paper is exposed under a transparent original and after development with ammonia, a

well contrasted violet red line print is obtained.

4-acetylaminoimidazole (formula 8) is obtained by the reaction of acetic anhydride and 4-nitroimidazole in the presence of stannous chloride as described in Hunter and Nelson, Canadian Journal Research, 1941 19B, 300 and Chemical Abstracts 1942, 36, 1 321. This product has a melting point of 230C; its theoretical proportion of nitrogen: N% is 33.5 8.

EXAMPLE III A transparent vegetable tracing paper is coated with an aqueous solution of the following composition:

Citric acid 3g Ethyl alcohol 3cc Triethylene glycol 3cc 1,2-dimethyl S-ethoxycarbonylamineimidazole (formula 12) lg Double chloride of zinc and p-diethyl aminobenzene diazonium 2g Water 100cc After drying, this paper is exposed under a transparent original and, after development with ammonia, a well contrasted orange brown line print is obtained which can be used as a counter negative.

The 1,2-dimethyl 5-ethoxycarbonylaminoimidazole (formula 12) is prepared in the following way by an original synthesis:

2-methyl 5-anilinocarbonylimidazole is prepared according to the Fargher and Pyman method, Journal Chemical Society, 1919, 229. This product is treated with 49% hydrobromic acid to obtain 2- methylimidazole S-carboxylic acid, which, in a methanol solution, is treated with gaseous hydrochloric acid to yield 2-methyl 5-methoxycarbonyl-imidazole.

This latter product is treated with diazomethane, and N-methyl N-nitroso p-toluene-sulfamide in alcoholether solution and in the presence of potash to yield 1,2-dimethyl 5-carbohydrazidoimidazole.

By treating this latter product with sodium nitrite in a hydrochloric medium, 1,2-dimethyl 5-azidocarbonylimidazole is obtained which, when treated with hot absolute ethanol, yields the desired product: 1,2- dimethyl 5-ethoxycarbonylaminoimidazole. The melting point of the latter is 122C; its theoretical proportion of nitrogen: N% is 23.12.

EXAMPLE IV The procedure in Example 3 is followed, replacing the 1,2-dimethyl S-ethoxycarbonylaminoimidazole with 2-phenyl 4-acetylaminoimidazole (formula 10).

A brownish red line print is thereby obtained, presenting a good covering power which can be used as a counter negative.

The 2-phenyl 4-acetylaminoimidazole (formula 10) is prepared according to the method of Julia and Hunyh Dinh Tam, Bulletin de la Societe Chimique de France, 1971, 4,1303.

EXAMPLE V The procedure in Example II is followed, replacing the 4-acetylaminoimidazole with 2-phenyl 4- acetylaminoimidazole (formula 10).

A well contrasted violet line on a white background is thereby obtained.

It should be apparent that the foregoing examples establish the novel characteristics of the method of the present invention. While the present invention has been primarily described by reference to the foregoing exemplification and description of the preferred embodiments, it should be understood that the present invention should in no way be limited thereto but rather must be construed as broadly as all or any equivalents thereof.

What is claimed is:

l. A two component diazo-type material suitable for making diazo-type reproductions comprising a base having a layer thereon consisting essentially of an acid stabilized mixture of at least one light-sensitive diazonium compound and at least one imidazole coupler compound selected from the group consisting of 2-mercaptoimidazole, 2-methylmercaptoimidazole, 2-ethylmercaptoimidazole, Z-acetylaminoimidazole, bis-(2- imidazolyl) 1,5-dithiopentane, 2-sulfamylimidazole, 2-phenacylthioimidazole, 4-acetylaminoimidazole, 1-

methyl 2-mercaptoimidazole 2-phenyl 4- acetylaminoimidazole hydrochloride, 2 ,5 diphenylimidazole, and 1 ,2-dimethyl S-ethoxycarbonylaminoimidazole and mixtures thereof.

2. The two component diazo-type material of claim 1 wherein said light-sensitive diazonium compound is a diazotized paraphenylene diamine or a salt thereof.

3. The two component system of claim 1 wherein said imidazole coupler compound is selected from the group consisting of 2-methylmercaptoimidazole, 2- ethylmercaptoimidazole, bis-( 2-imidazolyl)- l ,S-dithioperitane, 4-acetylaminoimidazole, 2-phenyl 4- acetylaminoimidazole hydrochloride, and 1,2-dimethyl 

1. A TWO COMPONENT DIAZO-TYPE MATERIAL SUITABLE FOR MAKING DIAZO-TYPE REPRODUCTIONS COMPRISING A BASE HAVING A LAYER THEREON CONSISTING ESSENTIALLY OF AN ACID STABLIZED MIXTURE OF AT LEAST ONE LIGHT-SENSITIVE DIAZONIUM COMPOUND AND AT LEAST ONE IMIDAZOLE COUPLER COMPOUND SELECTED FROM THE GROUP CONSISTING OF 2-MERCAPTOIMIDAZOLE, 2-METHYLMERCAPTOIMIDAZOLE, 2-ETHYLMERCAPTIOIMIDAZOLE, 2ACETYLAMINOIMIDAZOLE, BIS-(2-IMIDAZOLY) 1,5-DITHIOPENTANE, 2-SULFAMYLIMIDAZOLE, 2-PHENACYLTHIOIMIDAZOLE, 4ACETYLAMINOIMIDAZOLE, 1-METHYL 2-MERCAPTOIMIDAZOLE, 2-PHENYL 4-ACETYLAMINOIMIDAZOLE HYDROCHLORIDE, 2,5DIPHENYLIMIDAZOLE, AND 1,2-DIMETHYL 5-ETHYOXYCARBONYLAMINOIMIDAZLE AND MIXTURES THEREOF.
 2. The two component diazo-type material of claim 1 wherein said light-sensitive diazonium compound is a diazotized paraphenylene diamine or a salt thereof.
 3. The two component system of claim 1 wherein said imidazole coupler compound is selected from the group consisting of 2-methylmercaptoimidazole, 2-ethylmercaptoimidazole, bis-(2-imidazolyl)-1,5-dithiopentane, 4-acetylaminoimidazole, 2-phenyl 4-acetylaminoimidazole hydrochloride, and 1,2-dimethyl 5-ethoxycarbonylaminoimidazole. 